Cellulose is probably the most abundant biopolymer on Earth, and it is considered to be an important component in a future, sustainable and bio-based economy.
However, for materials based on cellulose fibers to be able to replace materials with higher ecological footprint (e.g. petroleum-based plastics), they need in many applications to provide an oxygen barrier.
Larsson et al. (Biomacromolecules 2014, 15, 2218-2223) describes the fabrication and characterization of nanocomposite films made of core-shell modified cellulose nanofibrils (CNFs) surrounded by a shell of ductile dialcohol cellulose, created by heterogeneous periodate oxidation followed by borohydride reduction of the native cellulose in the external parts of the individual fibrils. The oxidation with periodate selectively produces dialdehyde cellulose, and the process did not increase the charge density of the material. Yet the modified cellulose fibers could easily be homogenized to CNFs shown to be 0.5-2 μm long and 4-10 nm wide. Films were fabricated by slow filtration. At a relative humidity of 80%, the films acted as a good oxygen barrier.
A major drawback the produced CNFs is however that they are very difficult to dewater and film formation times of several hours are common, which significantly limits their use in industrial scale processes.
At the same time, the general understanding in the field has been that materials based on cellulose fibers, such as paper materials, cannot exhibit satisfactory oxygen barrier properties, especially not at a high relative humidity. It has been believed that the fibrous nature of such materials prevents the formation of structures that are dense enough to prevent penetration by gaseous oxygen.